The present invention relates to apparatus for the control of a switch in an AC supply line and in particular, but not exclusively, for use with incandescent, halogen and fluorescent lamps.
In known electrical wiring schemes for lamps, the LIVE wire is usually singularly routed to the wall switch box for reasons of practicality, ease and economics. The absence of the NEUTRAL wire from the wall switch box excludes the possibility to derive a DC supply from the AC supply via the LIVE wire within the same switch box location by conventional means of a transformer which may be used for powering electronic circuits including control circuits, remote control receivers, ambient light controls, RF control receivers, timer controls and motion detection controls.
A switch circuit has been exposed in the prior art to derive a DC voltage from the LIVE wire while periodically switching the AC supply to the connected lamp load. The method employs a DC voltage derivation circuit in parallel with a solid state switch, and in series with said load along the LIVE wire. Such a switch circuit is marketed by X-10, Inc (USA). For the switch circuit to work, it is required that the lamp load is a pure resistance-which lies within an ohmic range in order for the DC voltage derived to be sufficiently high to operate the electronic circuits, while maintaining the power below a safety level such that excessive heat dissipation from the electronic circuits does not occur. This inherent disadvantage therefore restricts the application of the switch circuit to the electronic controlled switching of purely resistive lamp loads such as incandescent or filament lamps.